Rotor brakes, in particular those associated with a helicopter, are typically designed to offer multiple functions. Dynamical braking refers to the braking required to stop the rotor quickly once the engine is switched off. At the start of dynamical braking the rotor is typically rotating. Parking braking refers to the engagement of the brake to lock the rotor and prevent unwanted rotor rotation, for example windmill effects. At the start of parking braking the rotor is typically not rotating, or maybe rotating a limited amount, e.g. due to windmill effects. A further function may be referred to as static braking, which refers to engagement of the brake, soon after which at least one engine is switched on. During static braking the brake holds the rotor against rotation and must be able to counter the motor torque without slippage of the rotor. At the start of static braking the rotor is typically not rotating.
As may be appreciated, the load requirements for static braking are often higher than those needed for dynamical and/or parking braking, due to the additional torque applied by the motor. Furthermore, it should be noted that if brake slippage occurs during static braking, and while the engine is on, safety may be compromised due to overheating.
Braking systems for rotors typically employ a brake disc attached to the rotor, and opposed friction surfaces either side of the brake disc that are configured to come together to contact the brake disc and apply a braking force. A caliper may hold the friction surfaces in position and be connected to an actuator adapted to control the application of the braking force. The current conventional arrangements typically use a mechanical, hydraulic or electric actuator. The conventional arrangements may have certain reliability issues, as well as increased design and manufacturing costs.
It is desired to provide an improved brake device for a rotor, such as a helicopter rotor, with a particular focus on the actuation of the brake.